In general, a storage device is connected to a host device (or expander) via an interface bus (host interface bus), such as a serial attached SCSI (SAS) bus or a serial AT attachment (SATA) bus. As a standard of such an interface bus, new power disable specifications are developed. The new power disable specifications are associated with device power management functions. In accordance with the new power disable specifications, an initiator (e.g., the host device) can disable power supply to main elements of the storage device as a target, which include a storage controller.
When a hang-up occurs in the interface bus, it is possible that a storage controller in the storage device is also hung up. According to the new power disable specifications, if the initiator (host device) determines that the interface bus is hung up, the host device asserts a power disable signal PWDIS supplied to the target (i.e., the storage device). When the signal PWDIS is asserted, the storage device should execute processing appropriately even if the storage controller of the storage device is hung up.